Commit 79caa362 authored by Nicolas Saenz Julienne's avatar Nicolas Saenz Julienne
Browse files

pwm: Add Raspberry Pi Firmware based PWM bus 



Adds support to control the PWM bus available in official Raspberry Pi
PoE HAT. Only RPi's co-processor has access to it, so commands have to
be sent through RPi's firmware mailbox interface.

Signed-off-by: default avatarNicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent a953e68e

drivers/pwm/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -423,6 +423,15 @@ config PWM_PXA 
	  To compile this driver as a module, choose M here: the module

	  will be called pwm-pxa.



config PWM_RASPBERRYPI_POE

	tristate "Raspberry Pi Firwmware PoE Hat PWM support"

	# Make sure not 'y' when RASPBERRYPI_FIRMWARE is 'm'. This can only

	# happen when COMPILE_TEST=y, hence the added !RASPBERRYPI_FIRMWARE.

	depends on RASPBERRYPI_FIRMWARE || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)

	help

	  Enable Raspberry Pi firmware controller PWM bus used to control the

	  official RPI PoE hat



config PWM_RCAR

	tristate "Renesas R-Car PWM support"

	depends on ARCH_RENESAS || COMPILE_TEST

drivers/pwm/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ obj-$(CONFIG_PWM_MXS) += pwm-mxs.o 
obj-$(CONFIG_PWM_OMAP_DMTIMER)	+= pwm-omap-dmtimer.o

obj-$(CONFIG_PWM_PCA9685)	+= pwm-pca9685.o

obj-$(CONFIG_PWM_PXA)		+= pwm-pxa.o

obj-$(CONFIG_PWM_RASPBERRYPI_POE)	+= pwm-raspberrypi-poe.o

obj-$(CONFIG_PWM_RCAR)		+= pwm-rcar.o

obj-$(CONFIG_PWM_RENESAS_TPU)	+= pwm-renesas-tpu.o

obj-$(CONFIG_PWM_ROCKCHIP)	+= pwm-rockchip.o

drivers/pwm/pwm-raspberrypi-poe.c

0 → 100644
+206 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Copyright 2021 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>

 * For more information on Raspberry Pi's PoE hat see:

 * https://www.raspberrypi.org/products/poe-hat/

 *

 * Limitations:

 *  - No disable bit, so a disabled PWM is simulated by duty_cycle 0

 *  - Only normal polarity

 *  - Fixed 12.5 kHz period

 *

 * The current period is completed when HW is reconfigured.

 */



#include <linux/module.h>

#include <linux/of.h>

#include <linux/platform_device.h>

#include <linux/pwm.h>



#include <soc/bcm2835/raspberrypi-firmware.h>

#include <dt-bindings/pwm/raspberrypi,firmware-poe-pwm.h>



#define RPI_PWM_MAX_DUTY		255

#define RPI_PWM_PERIOD_NS		80000 /* 12.5 kHz */



#define RPI_PWM_CUR_DUTY_REG		0x0



struct raspberrypi_pwm {

	struct rpi_firmware *firmware;

	struct pwm_chip chip;

	unsigned int duty_cycle;

};



struct raspberrypi_pwm_prop {

	__le32 reg;

	__le32 val;

	__le32 ret;

} __packed;



static inline

struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)

{

	return container_of(chip, struct raspberrypi_pwm, chip);

}



static int raspberrypi_pwm_set_property(struct rpi_firmware *firmware,

					u32 reg, u32 val)

{

	struct raspberrypi_pwm_prop msg = {

		.reg = cpu_to_le32(reg),

		.val = cpu_to_le32(val),

	};

	int ret;



	ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,

				    &msg, sizeof(msg));

	if (ret)

		return ret;

	if (msg.ret)

		return -EIO;



	return 0;

}



static int raspberrypi_pwm_get_property(struct rpi_firmware *firmware,

					u32 reg, u32 *val)

{

	struct raspberrypi_pwm_prop msg = {

		.reg = reg

	};

	int ret;



	ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,

				    &msg, sizeof(msg));

	if (ret)

		return ret;

	if (msg.ret)

		return -EIO;



	*val = le32_to_cpu(msg.val);



	return 0;

}



static void raspberrypi_pwm_get_state(struct pwm_chip *chip,

				      struct pwm_device *pwm,

				      struct pwm_state *state)

{

	struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);



	state->period = RPI_PWM_PERIOD_NS;

	state->duty_cycle = DIV_ROUND_UP(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,

					 RPI_PWM_MAX_DUTY);

	state->enabled = !!(rpipwm->duty_cycle);

	state->polarity = PWM_POLARITY_NORMAL;

}



static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,

				 const struct pwm_state *state)

{

	struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);

	unsigned int duty_cycle;

	int ret;



	if (state->period < RPI_PWM_PERIOD_NS ||

	    state->polarity != PWM_POLARITY_NORMAL)

		return -EINVAL;



	if (!state->enabled)

		duty_cycle = 0;

	else if (state->duty_cycle < RPI_PWM_PERIOD_NS)

		duty_cycle = DIV_ROUND_DOWN_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,

						RPI_PWM_PERIOD_NS);

	else

		duty_cycle = RPI_PWM_MAX_DUTY;



	if (duty_cycle == rpipwm->duty_cycle)

		return 0;



	ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,

					   duty_cycle);

	if (ret) {

		dev_err(chip->dev, "Failed to set duty cycle: %pe\n",

			ERR_PTR(ret));

		return ret;

	}



	rpipwm->duty_cycle = duty_cycle;



	return 0;

}



static const struct pwm_ops raspberrypi_pwm_ops = {

	.get_state = raspberrypi_pwm_get_state,

	.apply = raspberrypi_pwm_apply,

	.owner = THIS_MODULE,

};



static int raspberrypi_pwm_probe(struct platform_device *pdev)

{

	struct device_node *firmware_node;

	struct device *dev = &pdev->dev;

	struct rpi_firmware *firmware;

	struct raspberrypi_pwm *rpipwm;

	int ret;



	firmware_node = of_get_parent(dev->of_node);

	if (!firmware_node) {

		dev_err(dev, "Missing firmware node\n");

		return -ENOENT;

	}



	firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);

	of_node_put(firmware_node);

	if (!firmware)

		return dev_err_probe(dev, -EPROBE_DEFER,

				     "Failed to get firmware handle\n");



	rpipwm = devm_kzalloc(&pdev->dev, sizeof(*rpipwm), GFP_KERNEL);

	if (!rpipwm)

		return -ENOMEM;



	rpipwm->firmware = firmware;

	rpipwm->chip.dev = dev;

	rpipwm->chip.ops = &raspberrypi_pwm_ops;

	rpipwm->chip.base = -1;

	rpipwm->chip.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;



	platform_set_drvdata(pdev, rpipwm);



	ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,

					   &rpipwm->duty_cycle);

	if (ret) {

		dev_err(dev, "Failed to get duty cycle: %pe\n", ERR_PTR(ret));

		return ret;

	}



	return pwmchip_add(&rpipwm->chip);

}



static int raspberrypi_pwm_remove(struct platform_device *pdev)

{

	struct raspberrypi_pwm *rpipwm = platform_get_drvdata(pdev);



	return pwmchip_remove(&rpipwm->chip);

}



static const struct of_device_id raspberrypi_pwm_of_match[] = {

	{ .compatible = "raspberrypi,firmware-poe-pwm", },

	{ }

};

MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);



static struct platform_driver raspberrypi_pwm_driver = {

	.driver = {

		.name = "raspberrypi-poe-pwm",

		.of_match_table = raspberrypi_pwm_of_match,

	},

	.probe = raspberrypi_pwm_probe,

	.remove = raspberrypi_pwm_remove,

};

module_platform_driver(raspberrypi_pwm_driver);



MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");

MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");

MODULE_LICENSE("GPL v2");